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The bacillus of malignant edema stains well with ordi-
nary cold aqueous solutions of
the   anil in   dyes,   but   not   by
Gram's method.

The organism is not a difficult
one to secure in pure culture,
as has been said, generally con-
taminating tetanus cultures and
being much more easy to se-
cure by itself than its congener.
It is most easily obtained from
the edematous tissues of guinea-
pigs arid rabbits inoculated with

The colonies which develop
upon the surface of gelatin kept
free of oxygen appear to the
naked eye as small shining
bodies with liquid grayish-white
contents. They gradually in-
crease in circumference, but do
not change their appearance.
Under the microscope they ap-
pear filled with a tangled mass
of long filaments wrhich under a

FIG. 131.—Bacillus of malig-

- .   ..                      -,..«•     .,...,      .,   nant edema growing in gluco

high   power   exhibit individual  gelatin  Frankel and Pfeiffer).


movement.    The edges of the

colony have a fringed appearance, much like the hay or

potato bacillus.

In gelatin tube-cultures the characteristic growth can-
not be observed in a puncture, because of the air which
remains in the path of the wire. The best preparation
is made by heating the gelatin to expel the air it may
contain, inoculating while still liquid, then replacing the
air by hydrogen, and sealing the tube. In such a tube
the bacilli develop near the bottom. The appearance of
the growth is highly typical, as globular circumscribed
areas of cloudy liquefaction result (Fig. 131), and may con-